The brother of convicted cop killer Dexter Bostic hit the NYPD with a police brutality lawsuit today, accusing a team of detectives of wrongly arresting him and threatening to kill him in the hours after Officer Russel Timoshenko’s murder.

Frederick Bostic, 41, claims homicide detectives brutally beat him and hauled him into the 71st Precinct stationhouse in Brooklyn on July 9, 2007 as they hunted for his brother, the triggerman in the cold-blooded slaying of 23-year-old Timoshenko.

“You’re not going to make it out of here alive,” cops at the stationhouse taunted, according to the lawsuit filed in Brooklyn federal court. “You’ll only leave the precinct in a body bag.”

The detectives also threatened Bostic and his family “with retaliation if he did not help the police in their investigation concerning (his) brother,” the suit states.

Dexter Bostic, 36, is serving life without parole for gunning down Timoshenko during a traffic stop. His sister Nicole Bostic, 29, pleaded guilty to a misdemeanor charge of hindering prosecution for helping hide the murder weapon.

The day of the shooting, a team of detectives tracked down Frederick Bostic at the home of his friend Dawn Ashmore, 39, in East New York and threatened hurt them if they didn’t open the door, according to the suit.

Once inside, the detectives allegedly held a gun to Bostic’s face, threw him onto the floor and punched him as they searched the apartment.

They also threatened to take away Ashmore’s children and place them in the custody of the Administration of Children’s Services, according to the suit.

Both Bostic and Ashmore were taken into custody and released without facing charges.

They are seeking unspecified damages for false arrest, excessive force and an unlawful search.

The city’s Law Department they had not yet received the complaint and could not comment.